A man covers a certain distance by his own car. Had he moved 6 km/hr faster he would have taken 4 hours less. If he had moved 4 km/hr slower, he would have taken 4 hours more. The distance (in km) is
Question
A man covers a certain distance by his own car. Had he moved 6 km/hr faster he would have taken 4 hours less. If he had moved 4 km/hr slower, he would have taken 4 hours more. The distance (in km) is
Solution 1
Let's denote the following:
- The original speed of the man as 's' (in km/hr)
- The original time taken to cover the distance as 't' (in hours)
- The distance covered as 'd' (in km)
From the problem, we have two equations based on the relationship between speed, time, and distance:
- If the man moved 6 km/hr faster, he would have taken 4 hours less. This gives us the equation: d = (s + 6)(t - 4)
- If the man moved 4 km/hr slower, he would have taken 4 hours more. This gives us the equation: d = (s - 4)(t + 4)
Since both equations are equal to 'd', we can set them equal to each other and solve for 's':
(s + 6)(t - 4) = (s - 4)(t + 4)
Expanding both sides gives:
st - 4s + 6t - 24 = st + 4s - 4t - 16
Solving for 's' gives:
s = (30 + 2t) / 10
Substituting 's' into the first equation gives:
d = [(30 + 2t) / 10 + 6](t - 4)
Solving for 't' gives:
t = 10
Substituting 't' into the equation for 's' gives:
s = (30 + 2*10) / 10 = 5
Finally, substituting 's' and 't' into the equation for 'd' gives:
d = st = 5*10 = 50 km
So, the distance covered by the man is 50 km.
Solution 2
Let's denote the following:
- The original speed of the man as 's' km/hr
- The original time taken to cover the distance as 't' hours
- The distance covered as 'd' km
From the problem, we have two equations based on the conditions given:
-
If he moved 6 km/hr faster, he would have taken 4 hours less. This can be written as: d = (s+6)(t-4)
-
If he moved 4 km/hr slower, he would have taken 4 hours more. This can be written as: d = (s-4)(t+4)
Since both equations are equal to 'd', we can set them equal to each other and solve for 's' and 't':
(s+6)(t-4) = (s-4)(t+4)
Expanding both sides gives:
st - 4s + 6t - 24 = st + 4s - 4t - 16
Solving for 's' gives:
s = (30 + 2t) / 8
Substitute 's' into the equation d = st:
d = t * (30 + 2t) / 8
Solving for 't' gives:
t = 4 hours
Substitute 't' into the equation for 's':
s = (30 + 2*4) / 8 = 8.5 km/hr
Finally, substitute 's' and 't' into the equation for 'd':
d = 8.5 km/hr * 4 hours = 34 km
So, the distance covered is 34 km.
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